Division of Food Bioscience and Technology, College of Life Sciences and Biotechnology, Korea University, 5-1 Anam-dong, Sungbuk-gu, Seoul, 136-713, South Korea.

We sought to develop a method of decontaminating alfalfa sprouts of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella typhimurium without altering the seed germination capability using supercritical carbon dioxide (SC-CO(2)). Samples were treated with SC-CO(2) at 10, 15, or 20MPa and temperatures of 35, 40, or 45 degrees C for 5, 10, or 15min. The germination percentage was measured after three days of germination. Generally, treating seeds with SC-CO(2) at higher pressures, temperatures, or for longer treatment times resulted in greater microbial reductions than treatments at lower pressures, temperatures, or for shorter treatment times. SC-CO(2) treatment clearly reduced the microorganism levels in alfalfa seeds; in particular, treatment at 20MPa and 45 degrees C for 15min reduced levels of the three pathogens by >7.0log colony forming units (CFU)/g. However, SC-CO(2) treatment at a high pressure and high temperature, especially treatment at 20MPa and 40 or 45 degrees C, impaired the seed germination capability in some cases. Without impairing the germination capability, the maximum reduction level of E. coli O157:H7 was 3.51CFU/g with SC-CO(2) treatment at 15MPa and 35 degrees C for 10min. Maximum reductions of L. monocytogenes and S. typhimurium were 2.65 and 2.48log CFU/g, respectively, with treatment at 10MPa and 45 degrees C for 5min. Therefore, our results indicate that SC-CO(2) treatment can be used to effectively improve alfalfa seed safety.

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